The finale to the Burberry show at London fashion week in February. Photograph: David Levene for the Guardian

I'm going to stick my neck out and say we've seen the last of the Indian summer. Which means that from now until around the end of March, your coat will be the most important item in your wardrobe. And not only from a practical point of view: your coat will be your visual hello-how-are-you to the world. If all those statistics about how first impressions define you in the first 0.6 seconds or whatever are even a tiny bit true, then most people you meet in the next four-and-a-half months will have formed an indelible impression of you while your frozen fingers are still working on the top button.

Your party dress or Christmas Day outfit may seem significant to you, but the reality is that they will only be seen by people who are drunk, or have known you for years, or both. Drunk people who have either seen you grumpy every Monday morning this year or known you since your teen-goth phase are not likely to radically revise their opinion of you based on the on-trend burgundy tone of this year's party dress. Your coat, however, will define you whenever you walk into a room. What does yours say about you?

Duffel coat

The Peter Pan of coats, for boys and girls who don't want to grow up. The duffel coat is equal parts Paddington Bear adorable cuteness and teenage snark. This makes it perfect if, for instance, you are a member of Arctic Monkeys, but a bad idea if your career plan is to promote yourself as Sleek Young Executive Type in the office. The cosy hood and capacious pockets may be practical for buying cans of lager and waiting for the night bus to your mate's house, but is this the image you wish to project? Face it: you can't power-dress in a toggle.

Trenchcoat

The trench is no longer the fashion choice, but the status-symbol choice. Christoper Bailey's Burberry has played a fundamental role in convincing British women that coats can be ultra-desirable, wishlist-topping pieces rather than simply something to keep the rain off. The droopy, perenially damp coat-cupboard staple your granny called a raincoat is now reborn as the vaguely transatlantic sounding trench, flatteringly cut and with a dynamic this-season hemline.

Country coat

The Hoxton Farmer look refuses to die, and indeed has gone mass-market: TOWIE meets TOWID (The Only Way Is Dalston). Quilted nylon, waxed fabrics, pockets big enough to stuff a small game bird in and tweedy contrast collars have rolled out from hipster central to become a winter classic, as common in certain urban areas as they are in Berkshire. Practicality has a lot to do with it: farmers have to tramp around in the cold, and so do people who live in parts of east London that don't have tube stations. Similarly, they are practical both while driving tractors or cycling. But they have about as much wow factor as liking a flat white.

Parka

Want to look down-with-the-kids-street, yet glamorous at the same time? P Diddy, faced with this conundrum, alighted upon the idea of wearing white fur on big nights out. You can see how he thought it might work, but it had the unfortunate side-effect of making him look like an utter tool. The parka, in its fashion incarnation – a gold zip here, a faux-fur trim there (or rabbit – something to be aware of, even on the high street) – is the post-bling evening coat. Worn with killer heels, it locates you tantalisingly halfway between the high-maintenance type and the girl-next-door.

Leather sleeves

How to spot a Grazia reader at 50 paces this winter: leather sleeves on her coat. This look was all over the catwalks, and demonstrates commitment to fashion, because you are unlikely to get more than one winter's wear out of it. But the prevalence of high-street versions means this is not a status symbol. A trench makes you look like you have serious money; a leather sleeve makes you look like you spend your disposable income on fashion, and are gifted at sorting the wheat from the chaff in Zara. See also: the cape coat.

Mannish coat

If a leather sleeve says Grazia, an oversized androgynous classic wool coat says Italian Vogue. This is not necessarily better: your message may be more high-end, but on the other hand you lose 80% of your audience because most people won't understand what your coat is trying to tell them. Your gamble. A simply cut wool coat is the equivalent of having a self-imposed uniform of, say, black trousers and a white shirt. It makes you look low-maintenance in a disciplined, cerebral way rather than merely scruffy.

Bright coat

The Duchess of Cambridge's gift to the nation this winter will be bright red coats. Having been much photographed in a smart scarlet coat last week, Kate has designated wearing a coat in a colour to be acceptable style territory for timid would-be fashionables. Colour choice is everything here. Red is for sloanes (shades of the Boxing Day hunt), yellow and orange are for style bloggers, pink is for 14-year-olds and blue and green are for the rest of us. A coloured coat is not as impractical as you might think – if it clashes with your jumper, just button it up.

Princess coat

Duffel coats are for grownups who wish they were still 15 and hanging out behind the bike sheds; princess coats are for grownups who wish they were still 15 and at orchestra practice. And also, I don't mean to be rude, but, hello? Even the Duchess of Cambridge doesn't wear one of these any more. They look amazing on Alexa Chung, but so do leather shorts and cropped mohair sweaters, so that argument gets you nowhere. If you're too big for Bonpoint, you're too big for this coat.